New pathway can increase biofuel yields by 50 percent

A new synthetic metabolic pathway developed by chemical engineering researchers at the University of California, Los Angeles, can break down sugars quickly and efficiently.

The researchers believe that the rate in which this new pathway allows for the breakdown of glucose could lead to a 50 percent increase in the production of biofuels.

The new pathway is intended to replace the natural metabolic pathway known as glycolysis. Nearly all organisms use glycolysis to convert sugars into the molecular precursors that cells need.

Through glycolysis four of the six carbon atoms found in glucose are converted into two-carbon molecules known as acetyl-CoA – a precursor to biofuels such as ethanol and butanol.

While glycolysis converts four of the carbon atoms in glucose into a useful product, two of the available six are not utilized and are lost as carbon dioxide. This loss of two carbon atoms for every six is seen as a major gap in the efficiency of the process.

The U.C.L.A. research team’s synthetic pathway prevents this loss, being able to convert all six glucose carbon atoms into three molecules of acetyl-CoA.

“This pathway solved of the most of the significant limitations in biofuel production and biorefining: losing one-third of carbon from carbohydrate raw materials,” said principle investigator James Liao, U.C.L.A.”s Ralph M. Parsons Foundation Professor of Chemical Engineering and chair of the chemical and biomolecular engineering department.

The synthetic pathway developed by Mr. Liao and his colleagues uses enzymes found in several distinct pathways in nature. They called their new pathway non-oxidative glycolysis or NOG.

The team tested and confirmed NOG worked by genetically engineering E. coli to use the synthetic pathway. The engineered bacteria showed complete carbon conservation with the resulting acetyl-CoA molecules can be used to produce a desired chemical with higher carbon efficiency.

“We rerouted the most central metabolic pathway and found a way to increase the production of acetyl-CoA. Instead of losing carbon atoms to carbon dioxide, you can now conserve them and improve your yields and produce even more product,” explained Igor Bogorad, a graduate student in Mr. Liao’s laboratory.

“For biorefining, a 50 percent improvement in yield would be a huge increase. NOG can be a nice platform with different sugars for a 100 percent conversion to acetyl-CoA,” added Mr. Bogorad.

The researchers believe that NOG could easily be used to convert other kinds of sugar as well and even be used in biofuel production using photosynthetic microbes.